Near-infrared absorbing material fine particle dispersion, near-infrared absorber, near-infrared absorber laminate, and laminated structure for near-infrared absorption

ABSTRACT

A near-infrared absorbing material fine particle dispersion, a near-infrared absorber laminate, and a laminated structure for near-infrared absorption can exhibit higher near-infrared absorption property, compared to near-infrared fine particle dispersions, near-infrared absorber laminates, and laminated structures for near-infrared absorption, containing tungsten oxides or composite tungsten oxides according to the conventional art. Also, a near-infrared absorbing material fine particle dispersion in which composite tungsten oxide fine particles, each particle containing a hexagonal crystal structure, and a polymer compound with maleic anhydride introduced therein are contained in the polypropylene resin, and the near-infrared absorber laminate and the laminated structure for near-infrared absorption using the dispersion.

TECHNICAL FIELD

The present invention relates to a near-infrared absorbing material fineparticle dispersion, a near-infrared absorber, a near-infrared absorberlaminate, and a laminated structure for near-infrared absorption, havingtransparency in a visible light region and absorbability in anear-infrared region.

DESCRIPTION OF RELATED ART

It is generally known that a material containing free electrons exhibitsa reflection/absorption response due to plasma oscillation, with respectto an electromagnetic wave of a wavelength from 200 nm to 2,600 nm,which is close to solar radiation region. It is known that when theparticles of the powder forming the material are fine particles havingdiameters smaller than the wavelength of light, the geometric scatteringof the material in the visible light region (wavelength: 380 nm to 780nm) is reduced so that transparency in the visible light region isachieved.

The term “transparency” used in the present invention means high visiblelight transmittance with less scattering of light in the visible lightregion.

Meanwhile, the applicant has disclosed in Patent Document 1 an infraredshielding material fine particle dispersion in which tungsten oxide fineparticles and/or composite tungsten oxide fine particles, each particlehaving a particle size of 1 nm or more and 800 nm or less, are dispersedin a solid medium, the infrared shielding material fine particledispersion transmitting visible radiations while efficiently shieldingnear-infrared radiations, requiring no large-scale production equipmentfor film formation onto a substrate, nor heat treatment at hightemperature after film formation.

PRIOR ART DOCUMENT Patent Document

-   [Patent Document 1] Re-publication of PCT International Publication    No. WO2005/037932

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, after further studies, the present inventors have found thatthe dispersion described in Patent Document 1 has a problem in that thenear-infrared absorbing material fine particles may aggregate in thesolid medium so that the near-infrared absorption property decreases insome cases.

In view of such a situation, an object of the present invention is toprovide a near-infrared absorbing material fine particle dispersion, anear-infrared absorber, near-infrared absorber laminate, and a laminatedstructure for near-infrared absorption, which can exhibit highernear-infrared absorption property, compared to near-infrared fineparticle dispersions, near-infrared absorber laminates, and laminatedstructures for near-infrared absorption, containing tungsten oxides orcomposite tungsten oxides, according to the conventional art.

Means for Solving the Problem

In order to solve the above-described problems, the present inventorshave studied. The present inventors focused on polypropylene resin, as asolid medium, which has the lowest specific gravity among resins,extremely high workability, excellent strength, and high transparency.As a result of the studies, the present inventors have foundconfigurations of a near-infrared absorbing material fine particledispersion in which composite tungsten oxide fine particles and modifiedpolyolefin modified with one or more kinds selected from maleicanhydride and carboxylic anhydride (hereinafter sometimes referred to as“modified polyolefin”) are included in polypropylene resin, and thecomposite tungsten oxide fine particles are uniformly dispersed in thepolypropylene resin, and a near-infrared absorber, near-infraredabsorber laminate, and laminated structure for near-infrared absorption,using the near-infrared absorbing fine particle dispersion; and haveattained the present invention.

Namely, a first invention to solve the above-described problem provides

-   -   a near-infrared absorbing material fine particle dispersion,        including        -   composite tungsten oxide fine particles and        -   modified polyolefin modified with one or more kinds selected            from maleic anhydride and carboxylic anhydride, in            polypropylene resin.

A second invention provides

-   -   the near-infrared absorbing material fine particle dispersion        according to the first invention,    -   wherein the weight average molecular weight of the modified        polyolefin is 1,000 or more and 100,000 or less.

A third invention provides

-   -   the near-infrared absorbing material fine particle dispersion        according to the first or second invention,    -   wherein the acid number of the modified polyolefin is 1 mgKOH/mg        or more and 150 mgKOH/mg or less.

A fourth invention provides

-   -   the near-infrared absorbing material fine particle dispersion        according to any one of the first to third inventions,    -   wherein the dispersed particle size of the composite tungsten        oxide fine particle is 1 nm or more and 200 nm or less.

A fifth invention provides

-   -   the near-infrared absorbing material fine particle dispersion        according to any one of the first to fourth inventions,    -   wherein the composite tungsten oxide fine particles are        represented by general formula MxWyOz (where M element is one or        more kinds of elements selected from H, He, alkali metal,        alkaline earth metal, rare earth element, Mg, Zr, Cr, Mn, Fe,        Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl,        Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta,        Re, Be, Hf, Os, Bi, and I, W is tungsten, O is oxygen,        satisfying 0.20≤x/y≤0.37, 2.2≤z/y≤3.0).

A sixth invention provides

-   -   the near-infrared absorbing material fine particle dispersion        according to the fifth invention,    -   wherein the M element is one or more kinds of elements selected        from Cs and Rb.

A seventh invention provides

-   -   the near-infrared absorbing material fine particle dispersion        according to any one of the first to sixth inventions,    -   wherein the composite tungsten oxide fine particles include        composite tungsten oxide fine particles, each particle having a        hexagonal crystal structure.

An eighth invention provides

-   -   the near-infrared absorbing material fine particle dispersion        according to any one of the first to seventh inventions,    -   wherein the surface of the composite tungsten oxide fine        particle is coated with an oxide containing one or more kinds of        elements selected from Si, Ti, Zr, and Al.

A ninth invention provides

-   -   a near-infrared absorber,    -   wherein the near-infrared absorbing material fine particle        dispersion according to any one of the first to eighth        inventions is diluted and melt-kneaded with polypropylene resin        or a heterogeneous thermoplastic resin having compatibility with        polypropylene resin, and molded into any one shape selected from        a plate, a film, and a thin film.

A tenth invention provides

-   -   a near-infrared absorber laminate including the near-infrared        absorber according to the ninth invention laminated on a base        material.

An eleventh invention provides

-   -   a laminated structure for near-infrared absorption, including        the near-infrared absorber according to the ninth invention        present between two or more laminated plates selected from sheet        glass, plastic plate, and plastic plate containing fine        particles having near-infrared absorption function.

A twelfth invention provides

-   -   a laminated structure for near-infrared absorption,    -   wherein the near-infrared absorber laminate according to the        tenth invention is opposed to a laminated plate selected from        sheet glass, plastic plate, and plastic plate containing fine        particles having near-infrared absorption function, or is        present between two or more laminated plates selected from sheet        glass, plastic plate, and plastic plate containing fine        particles having near-infrared absorption function.

Advantage of the Invention

The near-infrared absorbing material fine particle dispersion accordingto the present invention provides a near-infrared absorbing materialfine particle dispersion, a near-infrared absorber, a near-infraredabsorber laminate, and a laminated structure for near-infraredabsorption, which exhibit higher near-infrared absorption property andmore excellent optical properties, compared to near-infrared absorbingmaterial fine particle dispersions, near-infrared absorbers,near-infrared absorber laminates, and laminated structures fornear-infrared absorption according to the conventional art.

DETAILED DESCRIPTION OF THE INVENTION

The near-infrared absorbing material fine particle dispersion accordingto the present invention includes the composite tungsten oxide fineparticles and the modified polyolefin modified with one or more kindsselected from maleic anhydride and carboxylic anhydride in polypropyleneresin, wherein the composite tungsten oxide fine particles are uniformlydispersed in the polypropylene resin.

In the near-infrared absorbing material fine particle dispersionaccording to the present invention having the above-describedconfiguration, the composite tungsten oxide fine particles which havebeen mechanically pulverized under predetermined conditions are keptdispersed in the polypropylene resin including the modified polyolefinmodified with one or more kinds selected from maleic anhydride andcarboxylic anhydride. The near-infrared absorbing material fine particledispersion according to the present invention having the configurationcan be used, for example, for providing the near-infrared absorberhaving a film-like shape, a thin film-like shape, or the like on thebase material having a low heatproof temperature such as a resinousmaterial to obtain the near-infrared absorber laminate. Furthermore,since large-scale equipment is not required for the formation of thenear-infrared absorber or the near-infrared absorber laminate, theproduction equipment is advantageously inexpensive.

Although the composite tungsten oxide which is the near-infraredabsorbing material according to the present invention is a conductivematerial, it is dispersed as fine particles in the matrix of a solidmedium so that particles are discretely dispersed. Therefore, thenear-infrared absorbing material according to the present inventionexhibits radio wave transmission, and has versatility, for example, asvarious window materials.

The near-infrared absorbing material fine particle dispersion accordingto the present invention is molded into any one shape selected from aplate, a film, and a thin film, to obtain the near-infrared absorberaccording to the present invention.

The near-infrared absorber laminate according to the present inventionincludes the near-infrared absorber laminated on a base material.

The laminated structure for near-infrared absorption according to thepresent invention is a combination of the near-infrared absorbingmaterial fine particle dispersion which takes a form of thenear-infrared absorber and is present between two or more laminatedplates selected from sheet glass, plastic plate, and plastic platecontaining fine particles having a solar radiation absorption function,and a laminated plate selected from sheet glass, plastic plate, andplastic plate containing fine particles having a solar radiationabsorption function.

The present invention will be described in detail hereafter in an orderof: 1. Polypropylene resin, 2. Modified polyolefin, 3. Compositetungsten oxide fine particles, 4. Method for producing compositetungsten oxide fine particles, 5. Near-infrared absorbing material fineparticle dispersion liquid and method for production thereof, 6.Near-infrared absorbing material fine particle dispersion and method forproduction thereof, 7. Near-infrared absorber and method for productionthereof, 8. Near-infrared absorber laminate and method for productionthereof, 9. Laminated structure for near-infrared absorption and methodfor production thereof, and 10. Summary.

1. Polypropylene Resin

The polypropylene resin used for the near-infrared absorbing materialfine particle dispersion according to the present invention is notparticularly limited. The polypropylene resin has the lowest specificgravity among thermoplastic resins, extremely high workability,excellent strength, and high transparency, and is also capable ofexhibiting the excellent near-infrared absorption property of thecomposite tungsten oxide of the present invention, and suitably enablesproduction of the near-infrared absorbing material fine particledispersion, the near-infrared absorber, the near-infrared absorberlaminate, and the laminated structure for near-infrared absorptionaccording to the present invention.

A polypropylene resin is a homopolymer of polypropylene, or a copolymerof propylene and one or more kinds of olefins. Note that a polymer inwhich unsaturated monocarboxylic acid or unsaturated dicarboxylic acidis copolymerized does not fall under the category of a polypropyleneresin.

In the above-described copolymer, examples of the constituent monomerother than propylene include ethylene, isobutylene, 1-butene, 2-butene,pentene, and hexene. The copolymer may be a random copolymer or a blockcopolymer. Examples of the copolymer include propylene-ethylene blockcopolymers and propylene-ethylene random copolymers.

The melt flow rate of the polypropylene resin according to the presentinvention at 230° C. under a load of 2,160 g is preferably 5 to 100 g/10minutes, more preferably 20 to 80 g/10 minutes, and still morepreferably 40 to 60 g/10 minutes.

2. Modified Polyolefin

The modified polyolefin used for the near-infrared absorbing materialfine particle dispersion according to the present invention is themodified polyolefin modified with one or more kinds selected from maleicanhydride and carboxylic anhydride.

The near-infrared absorbing material fine particle dispersion accordingto the present invention is obtained as a dispersion by adding andmelt-kneading the above-described modified polyolefin and the compositetungsten oxide fine particles which are the near-infrared absorbingmaterial fine particles described later in the polypropylene resin.

The modified polyolefin modified with one or more kinds selected frommaleic anhydride and carboxylic anhydride means the one including one ormore acidic groups selected from maleic anhydride and carboxylicanhydride added as side chains of the main chain of the polyolefinand/or at the end of the main chain of the polyolefin.

During melt-kneading of the near-infrared absorbing material fineparticles described later in the polypropylene resin, the modifiedpolyolefin promotes de-aggregation of the fine particles and furtherexhibits effect of securing the state of dispersion of the fineparticles in the polypropylene resin.

The addition amount of the modified polyolefin is preferably 1 part bymass or more and 2,000 parts by mass or less with respect to 100 partsby mass of the near-infrared absorbing material fine particles. It isbecause the above-described addition effect can be obtained with theaddition amount of 1 part by mass or more and the above-describedaddition effect is not saturated with the addition amount of 2,000 partsby mass or less.

A polymeric compound containing polyolefin having a polyethylene chainor a polypropylene chain as the main chain of the modified polyolefin ispreferred. In the modified polyolefin modified with maleic anhydride orthe like, it is considered that the main chain portion securescompatibility with the polyolefin resin or the like, and the side chainportion such as maleic anhydride secures the dispersibility of thenear-infrared absorbing material fine particles or the like.Furthermore, it is more preferable that the acid number is 1 mgKOH/mg ormore and the weight average molecular weight is 1,000 or more. Thereason is as follows. In the modified polyolefin, when the acid numberis 1 mgKOH/mg or more and the weight average molecular weight is 1,000or more, the near-infrared absorbing material fine particles can besufficiently de-aggregated and dispersed. On the other hand, in themodified polyolefin modified with maleic anhydride, the acid number of150 mgKOH/mg or less desirably provides well-balanced compatibility withpolyolefin resin or the like and dispersibility of the near-infraredabsorbing material fine particles or the like. With the weight averagemolecular weight of 100,000 or less, the viscosity does not becomeexcessive, providing good workability at the time of mixing.

Further, as the modified polyolefin, a commercially available resinmodifier can also be used. Preferred specific examples of thecommercially available resin modifier include: MODIC® P908, P553A, P555,P565 manufactured by Mitsubishi Chemical Corporation; UMEX® 1001, 1010manufactured by SANYOKASEI CO., LTD.; HI-WAX® NP0555A, NP50605A, Admer®QB550, QB515, QF500, QF550, QE060, QE840 manufactured by MitsuiChemicals, Inc.; OREVAC, BONDINE HX-8210 manufactured by Arkema.

3. Composite Tungsten Oxide Fine Particles

The composite tungsten oxide fine particles used for the near-infraredabsorbing material fine particle dispersion according to the presentinvention is represented by general formula MxWyOz (where M element isone or more kinds of elements selected from H, He, alkali metal,alkaline earth metal, rare earth element, Mg, Zr, Cr, Mn, Fe, Ru, Co,Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb,Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi, andI, W is tungsten, O is oxygen, satisfying 0.20≤x/y≤0.37, 2.2≤z/y≤3.0).

Generally, since there are no effective free electrons in tungstentrioxide (WO₃), absorption and reflection properties in thenear-infrared region are small, and the tungsten trioxide is noteffective as an infrared absorbing material. Here, it is known that freeelectrons are generated in the tungsten oxide by setting a ratio ofoxygen to tungsten in the tungsten trioxide to be smaller than 3.

M element is added to the tungsten oxide to obtain the compositetungsten oxide.

With this configuration, free electrons are generated in the compositetungsten oxide, and the absorption property derived from the freeelectrons are exhibited in the near-infrared region, and the compositetungsten oxide becomes effective as a near-infrared absorbing materialaround a wavelength of 1,000 nm. The near-infrared absorbing materialfine particle dispersion according to the present invention includes theabove-described composite tungsten oxide as the near-infrared absorbingmaterial fine particles, and the composite tungsten oxide absorbs thenear-infrared radiation and converts it into heat. Therefore, thenear-infrared absorbing material fine particle dispersion has thenear-infrared absorption property.

From this viewpoint, the near-infrared absorbing material fine particlesaccording to the present invention preferably include the compositetungsten oxide fine particles, each particle having a hexagonal crystalstructure.

For the composite tungsten oxide, since the above-described control ofthe amount of oxygen and the addition of an element that generates freeelectrons are used in combination, a more efficient near-infraredabsorbing material can be obtained. Specifically, in the compositetungsten oxide, general formula of the near-infrared absorbing material,in which control of the amount of oxygen and the addition of M elementthat generates free electrons are used in combination, is represented asMxWyOz (where M is the M element, W is tungsten, and O is oxygen),wherein a relationship of 0.001≤x/y≤1, preferably 0.20≤x/y≤0.37 issatisfied.

From the viewpoint of stability in the composite tungsten oxide with Melement added thereto, the M element is more preferably one or morekinds of elements selected from H, He, alkali metal, alkaline earthmetal, rare earth metal, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt,Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se,Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi, and I.

Moreover, from the viewpoint of stability in the MxWyOz with M elementadded thereto, the M element is more preferably one or more kinds ofelements selected from alkali metal, alkaline earth metal, rare earthelement, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn,Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb,V, Mo, Ta, and Re.

In addition, it is more preferable that the M element belongs to alkalimetal, alkaline earth metal element, transition metal element, 4B groupelement, or 5B group element from a viewpoint of improving opticalproperties and weather resistance as a near-infrared absorbing material.

Next, the value of z/y indicating the control of the amount of oxygen inthe MxWyOz will be described. In the infrared absorbing materialrepresented by MxWyOz, the value of z/y is preferably 2.2≤z/y≤3.0,because the same mechanism as the near-infrared absorbing materialrepresented by WyOz described above works depending on the value of z/y,and in addition, even at z/y=3.0, there is a supply of the freeelectrons due to the addition amount of the M element described above.

Here, Cs and Rb are the most preferred M elements. However, the Melement is not limited to the above Cs and Rb. Even when the M elementis an element other than Cs or Rb, it may be present as an added Melement in the hexagonal void formed by the units of WO₆.

When each composite tungsten oxide fine particle having the hexagonalcrystal structure has a uniform crystal structure, the addition amountof the added M element is 0.001≤x/y≤1, preferably 0.2≤x/y≤0.5, morepreferably 0.20≤x/y≤0.37, and most preferably x/y=0.33. The reason is asfollows. Theoretically, when satisfying z/y=3, x/y=0.33 is established,and the added M element is considered to be arranged in all hexagonalvoids.

Here, the present inventors have repeatedly studied in consideration offurther improving the near-infrared absorption function of the compositetungsten oxide fine particles, and have found a configuration in whichthe amount of the contained free electrons is further increased.

Namely, as a measure to increase the amount of the free electrons, theinventors have found a measure in which a mechanical treatment isapplied to the composite tungsten oxide fine particles to giveappropriate strain and deformation to the contained hexagonal crystals.In the hexagonal crystal given the appropriate strain and deformation,it is considered that the amount of the free electrons increases due toa change in an overlapping state of electron orbitals in the atomsconstituting the crystallite structure.

Therefore, the inventors have studied as follows: in a dispersion stepwhen producing the near-infrared absorbing material fine particledispersion liquid from the fine particles of the composite tungstenoxide produced by a firing step, the fine particles of the compositetungsten oxide are pulverized under predetermined conditions, therebygiving strain and deformation to the crystal structure and increasingthe amount of the free electrons, and the near-infrared absorptionfunction of the composite tungsten oxide fine particles is furtherimproved.

Further, it is found that each particle of the near-infrared absorbingmaterial fine particles according to the present invention preferablyhas a particle size of 1 nm or more and 200 nm or less, and morepreferably 100 nm or less. Then, from a viewpoint of exhibiting moreexcellent near-infrared absorption property, the particle size ispreferably 10 nm or more and 100 nm or less, more preferably 10 nm ormore and 80 nm or less, still more preferably 10 nm or more and 60 nm orless, and most preferably 10 nm or more and 40 nm or less. When theparticle size is in the range of 10 nm or more and 40 nm or less, themost excellent near-infrared absorption property is found to beexhibited.

The particle size used herein is an average value of the diameters ofthe individual near-infrared absorbing material fine particles which arenot aggregated, that is, an average value of the primary particle sizes,and is the average particle size of the near-infrared absorbing materialfine particles contained in the near-infrared absorbing material fineparticle dispersion described later. Therefore, the particle size doesnot include the diameter of the aggregate of the composite tungstenoxide fine particles, and is different from the dispersed particle size.

The average particle size is calculated from an electron microscopeimage of the near-infrared absorbing material fine particles.

The average particle size of the composite tungsten oxide fine particlescontained in the infrared absorbing material fine particle dispersioncan be obtained by measuring the primary particle sizes of 100 compositetungsten oxide fine particles using an image processing device andcalculating the average value thereof, from a transmission electronmicroscope image of thinned samples of the composite tungsten oxide fineparticles taken out by cross-section processing. A microtome, a crosssection polisher, a focused ion beam (FIB) apparatus, or the like can beused for cross-section processing for taking out the thinned samples.

Further, it is found that the composite tungsten oxide fine particle ispreferably a single crystal.

The fact that the composite tungsten oxide fine particle is a singlecrystal can be confirmed from an electron microscope image by atransmission electron microscope or the like in which no crystal grainboundaries are observed inside each fine particle, and only uniformlattice fringes are observed. Further, the fact that the amorphous phasevolume ratio is 50% or less in the composite tungsten oxide fineparticles can be confirmed from the same electron microscope image inwhich uniform lattice fringes are observed throughout the fineparticles, and there are almost no unclear lattice fringes. Therefore,the amorphous phase volume ratio in the composite tungsten oxide fineparticles can be confirmed from the observation of the ratio of theregion in which uniform lattice fringes are observed in the fineparticles to the region in which there are unclear lattice fringes.

Further, since the amorphous phase exists on the outer periphery of eachfine particle in many cases, the volume ratio of the amorphous phase canbe calculated by paying attention to the outer periphery of each fineparticle in many cases. For example, in a spherical composite tungstenoxide fine particle, when the amorphous phase with unclear latticefringes exists in a layered manner on the outer periphery of the fineparticle, the amorphous phase volume ratio in the composite tungstenoxide fine particles is 50% or less, as long as the thickness of thelayer is 10% or less of the particle size.

The near-infrared absorbing material fine particle dispersion containingthe composite tungsten oxide fine particles according to the presentinvention greatly absorbs light in the near-infrared region,particularly around the wavelength of 1,000 nm, and thus theirtransmission color tone is frequently blue to green.

Furthermore, it is necessary to consider the aggregation of thenear-infrared absorbing material fine particles and the dispersedparticle size of the near-infrared absorbing material fine particles,for the light scattering in the near-infrared absorbing material fineparticle dispersion described later in “6. Near-infrared absorbingmaterial fine particle dispersion, and method for production thereof.”Further, the dispersed particle size of the near-infrared absorbingmaterial fine particle can be selected depending on the intended use.

The dispersed particle size of the above-described near-infraredabsorbing material fine particle is a concept including a diameter of anaggregate of the composite tungsten oxide fine particles, which isdifferent from the concept of the particle size of the above-describednear-infrared absorbing material according to the present invention.

First, when used for applications while maintaining transparency, it ismore preferable to have a dispersed particle size of 800 nm or less. Itis because particle with a dispersed particle size smaller than 800 nmcan maintain the visibility in the visible light region withoutcompletely shielding light due to scattering, and at the same timeefficiently maintain the transparency. Particularly, when thetransparency of the visible light region is focused, it is preferable tofurther consider the scattering due to particles.

When the reduction of the scattering due to the particles is focused,the dispersed particle size is preferably 200 nm or less, morepreferably 10 nm or more and 200 nm or less, and still more preferably10 nm or more and 100 nm or less. The reason is as follows. When thedispersed particle size is small, the infrared absorbing layer can beprevented from looking like fogged glass and thus losing cleartransparency due to geometric or Mie scattering. In other words, thedispersed particle size of 200 nm or less corresponds to a region wherethe Rayleigh scattering is strong with the above-described geometricalscattering or Mie scattering being reduced. In the Rayleigh scatteringregion, the scattered light is in proportion to the sixth power of thedispersed particle size. Therefore, with the decrease in the dispersedparticle size, the scattering is reduced and the transparency isimproved. In addition, when the dispersed particle size is 100 nm orless, the scattered light extremely decreases, which is preferable. Fromthe viewpoint of avoiding light scattering, the smaller dispersedparticle size is more preferable. When the dispersed particle size is 10nm or more, industrial production is easy.

When the above-described dispersed particle size is 800 nm or less, thehaze value of the near-infrared absorbing material fine particledispersion in which the near-infrared absorbing material fine particlesare dispersed in a medium can be reduced to 10% or less at the visiblelight transmittance of 85% or less. In particular, when the dispersedparticle size is 100 nm or less, the haze value can be reduced to 1% orless.

The dispersed particle size of the near-infrared absorbing fine particleaccording to the present invention is preferably 800 nm or less. This isbecause the near-infrared absorption of the composite tungsten oxidewhich is a near-infrared absorbing fine particle is based on the lightabsorption and scattering peculiar to nanoparticles called “localizedsurface plasmon resonance”.

In other words, when the dispersed particle size of the compositetungsten oxide is 800 nm or less, localized surface plasmon resonanceoccurs, and the near-infrared absorbing fine particles efficientlyabsorb near-infrared radiations irradiated on the near-infraredabsorbing material fine particle dispersion according to the presentinvention and easily convert them into thermal energy.

When a dispersed particle size is 200 nm or less, the localized surfaceplasmon resonance becomes stronger and the irradiated near-infraredradiation is absorbed more strongly, which is more preferable.

Further, when the dispersed particle size of the near-infrared absorbingfine particle according to the present invention is 200 nm or less, thenear-infrared absorption property and transparency can be maintained.

Further, the near-infrared absorber produced by dispersing thenear-infrared absorbing material fine particles in an appropriate solidmedium or on the surface of the solid medium can efficiently absorbsolar radiation, particularly light in the near-infrared region, withoututilizing a light interference effect and at the same time transmitslight in the visible light region, compared to a layer produced by a drymethod like a vacuum deposition method such as a sputtering method, avapor deposition method, an ion plating method, and a chemical vapordeposition method (CVD method), or a layer produced by a CVD method or aspraying method.

4. Method for Producing Composite Tungsten Oxide Fine Particles

The composite tungsten oxide fine particles represented by generalformula MxWyOz according to the present invention can be produced by asolid phase reaction method for applying heat treatment to a mixture ofa tungsten compound as a starting material of the tungsten oxide fineparticles and a simple substance or compound containing the M elementmixed at a ratio of 0.20≤x/y≤0.37 in a reducing gas atmosphere, or in amixed gas atmosphere of a reducing gas and an inert gas, or in an inertgas atmosphere. After passing through the heat treatment, the compositetungsten oxide fine particles, micronized by pulverization treatment orthe like so as to have a predetermined particle size, have sufficientnear-infrared absorbing power and have preferable properties asnear-infrared absorbing material fine particles.

As a tungsten compound which is a starting material for obtaining thecomposite tungsten oxide fine particles represented by theabove-described general formula MxWyOz according to the presentinvention, it is possible to use a mixed powder of one or more kinds ofpowders selected from tungsten trioxide powder, tungsten dioxide powder,or a hydrate of tungsten oxide, or tungsten hexachloride powder, orammonium tungstate powder, or a tungsten oxide hydrate powder obtainedby dissolving tungsten hexachloride in alcohol and drying, or a tungstenoxide hydrate powder obtained by dissolving tungsten hexachloride inalcohol, making it precipitated by adding water, and drying, or atungsten compound powder obtained by drying an aqueous ammoniumtungstate solution, and a metal tungsten powder, and powder of a simplesubstance or a compound containing the M element, compounded at a ratioof 0.20≤x/y≤0.37.

Further, when the tungsten compound as the starting material forobtaining the composite tungsten oxide fine particles is a solution or adispersion liquid, each element can easily be mixed uniformly.

From this viewpoint, it is more preferable that the starting material ofthe composite tungsten oxide fine particles is powder obtained by mixingan alcoholic solution of tungsten hexachloride or an aqueous solution ofammonium tungstate and a solution of a compound containing the Melement, and then drying the mixture.

From a similar viewpoint, it is also preferable that the startingmaterial of the composite tungsten oxide fine particles is powderobtained by mixing a dispersion liquid prepared by dissolving tungstenhexachloride in alcohol and then adding water to form a precipitate, andpowder of a simple substance or a compound containing the M element or asolution of the compound containing the M element, and then drying themixture.

Examples of the compound containing the M element include, but are notlimited to, a tungstate salt, a chloride salt, a nitrate salt, a sulfatesalt, an oxalate salt, an oxide, a carbonate salt, and a hydroxide ofthe M element. The compound which can be in a solution state may beacceptable. Further, in the industrial production of the compositetungsten oxide fine particles, when tungsten oxide hydrate powder ortungsten trioxide and a carbonate salt or hydroxide of M element areused, hazardous gases and the like are not generated at the stage of theheat treatment or the like, which is preferable for a production method.

Now, explanation will be given for heat treatment conditions to obtainthe composite tungsten oxide using a mixture of the tungsten compound,which is a starting material for obtaining the composite tungsten oxidefine particles, and a compound containing the M element.

First, the above-described mixture which is a starting material isheat-treated in a reducing gas atmosphere, or in a mixed gas atmosphereof a reducing gas and an inert gas, or in an inert gas atmosphere.

Among the heat treatment conditions, the preferable heat treatmentconditions in a reducing atmosphere include heat treatment of powder ina reducing gas atmosphere at 100° C. or more and 850° C. or less, thepowder being a mixture of the tungsten compound starting material and asimple substance or compound containing M element or obtained by mixingthe solution or dispersion liquid of the tungsten compound startingmaterial and the solution or dispersion liquid of the compoundcontaining the M element, and subsequently drying the mixture. When theheat treatment temperature is 100° C. or more, the reduction reactionproceeds sufficiently, which is preferable. Further, when thetemperature is 850° C. or less, the reduction does not proceedexcessively, which is preferable. The reducing gas is not particularlylimited, but is preferably H₂. When H₂ is used as the reducing gas, H₂as a constituent of the reducing atmosphere is preferably 0.1% by volumeor more, and more preferably 2% by volume or more. When H₂ is 0.1% byvolume or more, reduction can proceed efficiently.

Then, it is desirable that the thus obtained particles are furtherheat-treated at a temperature of 550° C. or more and 1,200° C. or lessin the inert gas atmosphere as needed, in order to improve thecrystallinity and to remove the adsorbed reducing gas. As the heattreatment conditions in the inert gas atmosphere, 550° C. or more ispreferred. The composite tungsten compound starting materialheat-treated at 550° C. or more exhibits sufficient conductivity. As theinert gas, it is preferable to use an inert gas such as Ar or N₂. Thefollowing heat treatment conditions are proposed for the production of acomposite tungsten oxide having good crystallinity. However, the heattreatment conditions vary depending on the starting material and thetype of the target compound, so the method is not limited to thefollowing method.

In order to produce the composite tungsten oxide having goodcrystallinity, a higher heat treatment temperature is more preferable,and the reduction temperature varies depending on the starting materialand the H₂ temperature at the time of reduction, but is preferably 600°C. to 850° C. Further, the subsequent heat treatment temperature in theinert atmosphere is preferably from 700° C. to 1,200° C.

The processing time for firing may be appropriately selected accordingto the temperature, but may be 5 minutes or more and 5 hours or less.The thus obtained composite tungsten oxide fine particles along with anappropriate solvent are charged and wet-pulverized in a device selectedfrom a bead mill, a ball mill, a sand mill, a paint shaker, anultrasonic homogenizer, and the like to micronize the composite tungstenoxide particles.

By this heat treatment, 2.2≤z/y≤3.0 is satisfied in the compositetungsten oxide.

On the other hand, the method for producing the composite tungsten oxideis not limited to the solid phase reaction method. By settingappropriate production conditions, the composite tungsten oxide can alsobe produced by a thermal plasma method. Examples of the productionconditions to be appropriately set include: a supply rate at the time ofsupplying the raw material into thermal plasma; a flow rate of a carriergas used for supplying the raw material; a flow rate of a plasma gas formaintaining a plasma region; and a flow rate of a sheath gas flowingjust outside the plasma region.

The heat treatment step for obtaining the composite tungsten oxide orthe composite tungsten oxide particles described above may be referredto as the first step according to the present invention.

A bulk body or the particles of the composite tungsten oxide obtained inthe above-described heat treatment step may be preferably micronizedthrough the near-infrared absorbing material fine particle dispersionliquid described later in “5. Near-infrared absorbing material fineparticle dispersion liquid and method for production thereof”. In theprocess of mixing the composite tungsten oxide particles with anappropriate solvent to obtain a near-infrared absorbing material fineparticle dispersion liquid, the near-infrared absorbing material fineparticle dispersion liquid is obtained while wet-pulverizing the mixtureto proceed the micronization of the near-infrared absorbing material. Inorder to obtain the composite tungsten oxide fine particles from thenear-infrared absorbing material fine particle dispersion liquid, asolvent may be removed by a known method.

In addition, the bulk body or particles of the composite tungsten oxidecan be micronized by a dry-micronization using a jet mill or the like.However, even in the case of the dry-micronization, it is needless tosay that the pulverization conditions (micronization conditions) capableof imparting a predetermined particle size to the resulting compositetungsten oxide particles is to be set. For example, when a jet mill isused, a jet mill having an air volume and a processing time that satisfyappropriate pulverization conditions may be selected.

The step for obtaining the near-infrared absorbing material fineparticles according to the present invention by micronizing thecomposite tungsten oxide or the composite tungsten oxide particles asdescribed above may be referred to as the second step according to thepresent invention.

It is preferable to coat the surface of the near-infrared absorbingmaterial fine particle which is the composite tungsten oxide fineparticle obtained in the above-described second step with an oxidecontaining one or more kinds of metals selected from Si, Ti, Zr and Al,from a viewpoint of improving the weather resistance. The coating methodis not particularly limited, but the surface of the near-infraredabsorbing material fine particle can be coated by adding an alkoxide ofthe above-described metal into a solution in which the near-infraredabsorbing material fine particles are dispersed.

5. Near-Infrared Absorbing Material Fine Particle Dispersion Liquid andMethod for Production Thereof

As described above, the near-infrared absorbing material fine particledispersion liquid according to the present invention is obtained bymixing and dispersing the composite tungsten oxide fine particlesobtained in the first step in an appropriate solvent. The solvent is notparticularly limited, and can be suitably selected according to coatingand kneading conditions, coating and kneading environments, and furtherin the case of containing inorganic binder or resin binder, according tothe binder. For example, water, and various organic solvents likealcohols such as ethanol, propanol, butanol, isopropyl alcohol, isobutylalcohol, diacetone alcohol; ethers such as methyl ether, ethyl ether,propyl ether; esters; ketones such as acetone, methyl ethyl ketone,diethyl ketone, cyclohexanone, isobutyl ketone; aromatic hydrocarbonssuch as toluene or the like can be used.

Further, an acid or alkali may be added to the dispersion liquid toadjust pH, as desired.

Furthermore, a resin monomer or oligomer may be used as the solvent.

Needless to say, it is also possible to add various kinds ofdispersants, surfactants, coupling agents and the like to furtherimprove the dispersion stability of the above-described compositetungsten oxide fine particles in the dispersion liquid.

The dispersant, surfactant, and coupling agent can be selected accordingto the intended use, but are preferably those having an amine-containinggroup, a hydroxyl group, a carboxyl group, or an epoxy group as afunctional group. These functional groups have effects of adsorbing onthe surface of the surface-treated near-infrared absorbing material fineparticles to prevent aggregation and uniformly dispersing the fineparticles. A polymer dispersant having any of these functional groups inthe molecule is more preferable.

As preferred specific examples of the commercially available dispersant,the following can be used: SOLSPERSE® 3000, 9000, 11200, 13000, 13240,13650, 13940, 16000, 17000, 18000, 20000, 21000, 24000SC, 24000GR,26000, 27000, 28000, 31845, 32000, 32500, 32550, 32600, 33000, 33500,34750, 35100, 35200, 36600, 37500, 38500, 39000, 41000, 41090, 53095,55000, 56000, 76500, and the like manufactured by Japan Lubrizol Co.,Ltd.;

Disperbyk®-101, 103, 107, 108, 109, 110, 111, 112, 116, 130, 140, 142,145, 154, 161, 162, 163, 164, 165, 166, 167, 168, 170, 171, 174, 180,181, 182, 183, 184, 185, 190, 2000, 2001, 2020, 2025, 2050, 2070, 2095,2150, 2155, Anti-Terra®-U, 203, 204, BYK®-P104, P104S, 220S, 6919, andthe like manufactured by BYK Japan KK;

EFKA®-4008, 4046, 4047, 4015, 4020, 4050, 4055, 4060, 4080, 4300, 4330,4400, 4401, 4402, 4403, 4500, 4510, 4530, 4550, 4560, 4585, 4800, 5220,6230, manufactured by EFKA Additives B. V.; JONCRYL®-67, 678, 586, 611,680, 682, 690, 819, JDX5050 and the like manufactured by BASF Japan;

TERPLUS® MD 1000, D 1180, D 1330 and the like manufactured by OtsukaChemical Co., Ltd.;

DIANAL® BR-87, 116, and the like manufactured by Mitsubishi ChemicalCorporation; and

AJISPER® PB-711, PB-821, PB-822, and the like manufactured by AjinomotoFine-Techno Co., Ltd.

The infrared absorbing material fine particle dispersion liquidcontaining 80 parts by weight or more of the solvent with respect to 100parts by weight of the near-infrared absorbing material fine particlescan easily ensure preserving property as a dispersion liquid and alsoensure workability during the subsequent production of the near-infraredabsorbing material fine particle dispersion.

The method for dispersing the composite tungsten oxide fine particles inthe solvent is not particularly limited as long as it can uniformlydisperse the fine particles in the dispersion liquid and prepare thecomposite tungsten oxide fine particles having the particle size of 800nm or less, preferably 200 nm or less, and still more preferably 10 nmor more and 100 nm or less. Examples include a bead mill, a ball mill, asand mill, a paint shaker, an ultrasonic homogenizer, and the like.

The mechanical dispersion treatment step using such a device facilitatesdispersion of the composite tungsten oxide fine particles in the solventand, at the same time, mutual collision of the composite tungsten oxideparticles and the like can facilitate micronization, giving strain anddeformation to the hexagonal crystal structure included in the compositetungsten oxide particles. Accordingly, an overlapping state of electronorbitals in the atoms constituting the crystal structure changes, sothat the amount of the free electrons increases.

The rate of progress of micronization of the composite tungsten oxideparticles varies depending on the device constant of the pulverizer.Therefore, it is important to carry out trial pulverization in advanceto obtain a pulverizer and pulverization conditions capable of impartinga predetermined particle size to the composite tungsten oxide fineparticle.

Even when the near-infrared absorbing material fine particles aremicronized via the near-infrared absorbing material fine particledispersion liquid and then the solvent is removed to obtain thedispersed powder of the near-infrared absorbing material fine particles,it is needless to say that pulverization conditions (micronizationconditions) capable of imparting a predetermined particle size are to beset. Since the dispersed powder is a kind of the dried and solidifiednear-infrared absorbing fine particle dispersion liquid and contains theabove-described dispersant, it can be re-dispersed in the solvent bymixing with an appropriate solvent.

The state of the near-infrared absorbing material fine particledispersion liquid according to the present invention can be confirmed bymeasuring the state of dispersion of the composite tungsten oxide fineparticles when the composite tungsten oxide fine particles are dispersedin the solvent. For example, the composite tungsten oxide fine particlesaccording to the present invention can be confirmed by sampling samplesfrom a liquid in which they exist as fine particles and aggregated fineparticles in the solvent, and performing measurement using variouscommercially available particle size distribution meters. As theparticle size distribution meter, for example, a known measuring devicesuch as ELS-8000 manufactured by Otsuka Electronics Co., Ltd. based onthe dynamic light scattering method can be used.

In addition, as for the crystal structure of the composite tungstenoxide fine particles, X-ray diffraction measurement is performed on thedispersed powder of the composite tungsten oxide fine particles obtainedby removing the solvent from the near-infrared absorbing material fineparticle dispersion liquid to specify the crystal structure included inthe fine particles.

From a viewpoint of exhibiting excellent near-infrared absorptionproperty, the crystallite size of the near-infrared absorbing fineparticle is preferably 1 nm or more and 200 nm or less, more preferably1 nm or more and 100 nm or less, and still more preferably 10 nm or moreand 70 nm or less. The measurement of the crystallite size usesmeasurement of the X-ray diffraction pattern by the powder X-raydiffraction method (0-20 method) and analysis by the Rietveld method. Ameasurement of the X-ray diffraction pattern can be performed using apowder X-ray diffraction apparatus (X′Pert-PRO/MPD manufactured bySpectris Corporation, PANalytical).

It is preferred that the dispersed particle size of the compositetungsten oxide fine particle is sufficiently fine, preferably 200 nm orless, more preferably 100 nm or less, from the viewpoint of the opticalproperties. Further, it is preferred that the composite tungsten oxidefine particles are uniformly dispersed.

The reason is as follows. When the dispersed particle size of thecomposite tungsten oxide fine particle is preferably 200 nm or less,more preferably 10 nm or more and 200 nm or less, and still morepreferably 10 nm or more and 100 nm or less, it is possible to avoid theproduced near-infrared absorber from becoming a grayish matter which hasmonotonously decreased transmittance.

The dispersed particle size of the near-infrared absorbing material fineparticle dispersion according to the present invention is a conceptindicating a particle size of a simple particle of the compositetungsten oxide fine particles and of an aggregated particle of thecomposite tungsten oxide fine particles, each particle being dispersedin the near-infrared absorbing material fine particle dispersion ornear-infrared absorber.

The dispersed particle size of the composite tungsten oxide fineparticle, which is the near-infrared absorbing material fine particle,in the near-infrared absorbing material fine particle dispersionaccording to the present invention can be obtained by measuring theparticle sizes of 100 composite tungsten oxide fine particles using animage processing device and calculating the average value thereof, froma transmission electron microscope image of thinned samples taken out ofthe near infrared absorbing material fine particle dispersion bycross-section processing.

A microtome, a cross section polisher, a focused ion beam (FIB)apparatus, or the like can be used for cross-section processing fortaking out the thinned samples. The dispersed particle size of thecomposite tungsten oxide fine particle contained in the near-infraredabsorbing material fine particle dispersion is the average value of thedispersed particle sizes of the composite tungsten oxide fine particleswhich are the near-infrared absorbing fine particles dispersed in asolid medium which is a matrix.

On the other hand, in the near-infrared absorbing material fine particledispersion liquid, the composite tungsten oxide fine particles aggregateinto coarse aggregates. When a large number of the coarsened particlesexist, such coarse particles become a light scattering source. As aresult, when the near-infrared absorbing material fine particledispersion liquid is formed into the near-infrared absorbing layer orthe near-infrared absorber, the cloudiness (haze) becomes higher, whichmay cause a decrease in visible light transmittance. Therefore, it ispreferable to avoid the formation of coarse particles of the compositetungsten oxide fine particles.

In order to obtain the near-infrared absorbing material fine particlesfrom the resulting near-infrared absorbing material fine particledispersion liquid, the solvent may be removed by a known method.However, the near-infrared absorbing material fine particle dispersionliquid is preferably dried under reduced pressure. Specifically, thenear-infrared absorbing material fine particle dispersion liquid may bedried under reduced pressure while stirring to separate the solventcomponent. The pressure value is appropriately selected at the time whenthe pressure is reduced in the drying step.

When the drying-under-reduced-pressure method is used, the efficiency ofremoving the solvent from the near-infrared absorbing material fineparticle dispersion liquid is improved, and the near-infrared absorbingmaterial fine particle dispersed powders according to the presentinvention are not exposed to high temperature for a long time.Accordingly, aggregation of the near-infrared absorbing material fineparticles dispersed in the dispersed powders does not occur, which ispreferable. Furthermore, the productivity of the near-infrared absorbingmaterial fine particles is enhanced, and the evaporated solvent can beeasily recovered, which is preferable from the viewpoint ofenvironmental consideration.

As equipment used in the drying process, those including, but notlimited to, vacuum flow dryers, vacuum heating and stirring crushers,vibration flow dryers, drum dryers, and the like are preferred from theviewpoint that heating and reducing pressure are possible and thedispersed powder can be easily mixed and recovered.

6. Near-Infrared Absorbing Material Fine Particle Dispersion and Methodfor Production Thereof

The near-infrared absorbing material fine particle dispersion accordingto the present invention includes the above-described near-infraredabsorbing material fine particles, the modified polyolefin modified withone or more kinds selected from maleic anhydride and carboxylicanhydride described above, and polypropylene resin.

When 80 parts by mass or more of polypropylene resin is contained withrespect to 100 parts by mass of the near-infrared absorbing materialfine particles, the near-infrared absorbing material fine particledispersion can be preferably formed.

When the near-infrared absorbing material fine particles aremelt-kneaded into polypropylene resin, the modified polyolefin modifiedwith one or more kinds selected from maleic anhydride and carboxylicanhydride described in “2. Modified polyolefin” and/or a resin modifierwhich contains a similar polymeric compound is added.

The addition amount of the modified polyolefin is preferably 1 part bymass or more and 2,000 parts by mass or less with respect to 100 partsby mass of the near-infrared absorbing material fine particles.

Specifically, the near-infrared fine particle dispersion liquid, thepolypropylene resin, and the modified polyolefin are kneaded at atemperature equal to or higher than the melting temperature of thepolypropylene resin, and then cooled to a predetermined temperature, toobtain the near-infrared absorbing material fine particle dispersion. Asa method for kneading, a twin-screw extruder, a single-screw extruder orthe like can be used.

As another method for obtaining the near-infrared absorbing materialfine particle dispersion, the solvent is removed from the near-infraredabsorbing material fine particle dispersion liquid to obtainnear-infrared absorbing material fine particle dispersed powders, whichmay be subsequently melt-kneaded with the polypropylene resin and themodified polyolefin.

It is also preferable to produce the near-infrared absorbing materialfine particle dispersion in the form of a masterbatch by adding anappropriate amount of a part, rather than a whole, of the solid mediumto be added, in the near-infrared absorbing fine particle dispersionaccording to the present invention.

When the near-infrared absorbing material fine particle dispersionaccording to the present invention is produced in the form of amasterbatch, a mixture of a solid medium containing the modifiedpolyolefin and the near-infrared absorbing material fine particles iskneaded in a bent-type single-screw or twin-screw extruder, andprocessed into pellets to provide the near-infrared absorbing materialfine particle dispersion according to the present invention in the formof a masterbatch.

The masterbatch pellets can be obtained by the most common method forcutting melt-extruded strands. Accordingly, examples of their shapeinclude a cylinder and a prism. Further, a so-called hot cut method canbe employed which directly cuts the melt-extrudate. In such a case, thepellet generally takes a shape close to a sphere.

As described above, the masterbatch according to the present inventioncan take any form or shape. However, the masterbatch pellet preferablyhas the same form and shape as those of the solid medium used fordilution when molding the near-infrared absorber described later.

Since the composite tungsten oxide fine particles maintain a dispersedstate in the near-infrared absorbing material fine particle dispersionaccording to the present invention, the near-infrared absorbing materialfine particle dispersion has the advantage of being applicable to a basematerial having a low heatproof temperature such as a resinous material,and inexpensive without requiring large-scale equipment in the formationof the near-infrared absorber.

In some cases, the average particle size of the composite tungsten oxidefine particle dispersed in the matrix of the polypropylene resin of thenear-infrared absorbing material fine particle dispersion (masterbatch)may be different from the dispersed particle size of the compositetungsten oxide fine particle dispersed in the near-infrared absorbingmaterial fine particle dispersion liquid used for forming thenear-infrared absorbing material fine particle dispersion. This isbecause aggregation of the composite tungsten oxide fine particles whichaggregate in the dispersion liquid is resolved when the near-infraredabsorbing material fine particle dispersion is obtained from thenear-infrared absorbing material fine particle dispersion liquid.

7. Near-Infrared Absorber and Method for Production Thereof

The near-infrared absorbing material fine particle dispersion accordingto the present invention is molded into any one shape selected from aplate, a film, and a thin film, to obtain the near-infrared absorberaccording to the present invention. On the other hand, the near-infraredabsorbing material fine particle dispersion according to the presentinvention in the form of a masterbatch is mixed with a predeterminedamount of the polypropylene resin medium which is a solid medium, or aheterogeneous thermoplastic resin medium having compatibility with thepolypropylene resin according to a known method, and molded into any oneshape selected from a plate shape, a film shape, and a thin film shape,according to a known method.

The near-infrared absorber according to the present invention moreefficiently absorbs solar radiation, especially light in thenear-infrared region, compared to the near-infrared absorber accordingto the conventional art, and at the same time exhibits excellent opticalproperty of maintaining high transmittance in the visible light region.Then the absorbed near-infrared radiations are converted into heat.

The near-infrared absorbing material fine particle dispersion accordingto the present invention can be used to obtain the near-infraredabsorber having excellent near-infrared absorption property.

The term near-infrared absorption property used in the present inventionis a concept indicating that light of a wavelength from 780 nm to 1,200nm in the near-infrared region is well absorbed.

The solar radiation includes various wavelengths, and can be roughlyclassified into ultraviolet, visible, and infrared radiations. Amongthem, infrared radiation is known to account for about 46%. Thenear-infrared absorbing material fine particles according to the presentinvention greatly absorb light in the near infrared region, particularlyin the vicinity of a wavelength of 1,000 nm.

Therefore, the near-infrared absorption property can be evaluated by thetransmittance of the solar radiation, that is, the solar transmittance.When the solar transmittance is low, light in the near-infrared regionis well-absorbed, so that it can be determined that the near-infraredabsorption property is excellent.

As a result, for example, when the film-like near-infrared absorberaccording to the present invention is attached to a window, thepenetration of solar heat into the room can be controlled whilemaintaining the brightness of the room.

The method has been explained in which a masterbatch of thenear-infrared absorbing material fine particle dispersion according tothe present invention is mixed with a predetermined amount of thepolypropylene resin which is a solid medium, or a heterogeneousthermoplastic resin medium having compatibility with the polypropyleneresin according to a known method, and molded into any one shapeselected from a plate shape, a film shape, and a thin film shape,according to a known method. However, the near-infrared absorbingmaterial fine particles according to the present invention can bedispersed in a solid medium which is a base material, not via amasterbatch.

In order to disperse the near-infrared absorbing material fine particlesin a solid medium, it is also preferable that the polypropylene resinwhich is the solid medium, or a heterogeneous thermoplastic resin mediumhaving compatibility with the polypropylene resin, is melted while thetemperature is raised to a temperature equal to or higher than a meltingtemperature thereof, and then 100 parts by mass of the near-infraredabsorbing material fine particles are mixed with 1 part by mass or moreand 2,000 parts by mass or less of the modified polyolefin, and thepolypropylene resin or a heterogeneous thermoplastic resin medium havingcompatibility with the polypropylene resin. The resultant can be moldedinto a film or a plate (board) by a predetermined method to obtain anear-infrared absorber.

A specific method for dispersing the near-infrared absorbing materialfine particles in the solid medium containing the polypropylene resin orthe heterogeneous thermoplastic resin having compatibility with thepolypropylene resin includes firstly mixing the solid medium, thenear-infrared absorbing material fine particle dispersion liquid aftermechanical pulverization under predetermined conditions, and themodified polyolefin modified with 1 part by mass or more and 2,000 partsby mass or less of one or more kinds selected from maleic anhydride andcarboxylic anhydride with respect to 100 parts by mass of thenear-infrared absorbing material fine particles; subsequentlyevaporating the dispersion solvent to obtain a mixture; thereafterheating the resulting mixture to about 280° C. which is a meltingtemperature of the solid medium, and mixing the melted polypropyleneresin or heterogeneous thermoplastic resin medium having compatibilitywith the polypropylene resin, the near-infrared absorbing material fineparticles, and the modified polyolefin modified with one or more kindsselected from maleic anhydride and carboxylic anhydride; and thereaftercooling to obtain the near-infrared absorbing material fine particledispersion.

Alternatively, the near-infrared absorbing material fine particles, andthe modified polyolefin modified with one or more kinds selected frommaleic anhydride and carboxylic anhydride may be penetrated from thesurface of the solid medium into the inside thereof to obtain thenear-infrared absorbing material fine particle dispersion.

As described above, the resulting near-infrared absorbing material fineparticle dispersion can be molded into a thin film, a film, or a plateby a predetermined method to obtain the near-infrared absorber accordingto the present invention.

8. Near-Infrared Absorber Laminate and Method for Production Thereof

In the near-infrared absorber laminate according to the presentinvention, the near-infrared absorber is laminated on a surface of apredetermined base material.

The near-infrared absorber laminate according to the present inventioncan be produced by forming the near-infrared absorber on the surface ofa predetermined base material.

The base material for the near-infrared absorber laminate may be eithera film or a board, as desired, and the shape is not limited. For thematerial of the transparent base material, PET, acrylic, urethane,polycarbonate, polyethylene, ethylene-vinyl acetate copolymer, vinylchloride, fluorine resin, or the like can be used depending on thepurposes. Besides resin, glass may be used.

9. Laminated Structure for Near-Infrared Absorption and Method forProduction Thereof

In one of the laminated structures for near-infrared absorptionaccording to the present invention, the near-infrared absorber moldedusing the near-infrared absorbing material fine particle dispersionaccording to the present invention is present between two or morelaminated plates selected from sheet glass, plastic plate, and plasticplate containing fine particles having near-infrared absorptionfunction.

In one of the laminated structures for near-infrared absorptionaccording to the present invention, the near-infrared absorber laminateis opposed to a laminated plate selected from sheet glass, plasticplate, and plastic plate containing fine particles having near-infraredabsorption function, or is present between two or more laminated platesselected from sheet glass, plastic plate, and plastic plate containingfine particles having near-infrared absorption function.

The transparent near-infrared absorbing laminate base material using thenear-infrared absorber according to the present invention may be in avariety of forms.

For example, a near-infrared absorbing laminated inorganic glass usingan inorganic glass as a transparent base material is obtained byattaching and integrating a plurality of opposing inorganic glass sheetswith a near-infrared absorber being sandwiched therebetween, by a knownmethod. The obtained near-infrared absorbing laminated inorganic glasscan be used as building materials such as roofing materials forcarports, stadiums, shopping malls, and airports, window materials, andthe like. In addition, it can also be used for car windows (roofwindows, quarter windows) and car windshields.

The above-described near-infrared absorber or near-infrared absorberlaminate according to the present invention can be sandwiched betweentwo or more opposing transparent base materials, or the near-infraredabsorber laminate according to the present invention can be opposed tothe transparent base material, to produce the laminated structure fornear-infrared absorption according to the present invention.

Similarly to the case using a transparent resin as the transparent basematerial and using the above-described inorganic glass, thenear-infrared absorbing layer according to the present invention can besandwiched between two or more opposing transparent base materialsselected from sheet glass, plastic, and plastic containing fineparticles having near-infrared absorption function, or the near-infraredabsorber laminate according to the present invention can be opposed tothe transparent base material, to produce the transparent near-infraredabsorbing laminated base material. The intended use is similar to thatof the near-infrared absorbing laminated inorganic glass.

Further, a near-infrared absorbing layer can be used alone depending onthe intended use. Of course, the transparent base material such asinorganic glass or transparent resin with the near-infrared absorbinglayer existing on either or both sides thereof can also be used as anear-infrared absorber laminate.

10. Summary

The infrared absorbing material fine particle dispersion, thenear-infrared absorber, the near-infrared absorber laminate, and thelaminated structure for near-infrared absorption according to thepresent invention more efficiently absorb solar radiation, especiallylight in the near-infrared region, compared to the near-infraredabsorbing material fine particle dispersions, near-infrared absorbers,and laminated structures for near-infrared absorption according to theconventional art, while exhibiting excellent optical properties, forexample, maintaining high transmittance in the visible light region.

The near-infrared absorber laminate produced by film formation on thebase material using the near-infrared absorbing material fine particledispersion according to the present invention, in which thenear-infrared absorbing material fine particles are dispersed in thepolypropylene resin or a heterogeneous thermoplastic resin havingcompatibility with the polypropylene resin, more efficiently absorbssolar radiation, particularly light in the near-infrared region,compared to a layer produced by a dry method like a vacuum depositionmethod such as a sputtering method, a vapor deposition method, an ionplating method, and a chemical vapor deposition method (CVD method),while exhibiting excellent optical properties, for example, maintaininghigh transmittance in the visible light region.

Further, the near-infrared absorber, near-infrared absorber laminate,and laminated structure for near-infrared absorption according to thepresent invention can be inexpensively produced without usinglarge-scale equipment such as vacuum equipment, and are industriallyuseful.

EXAMPLES

The present invention will be specifically described, with reference toexamples. However, the present invention is not limited thereto.

In the measurement of the crystallite size of the composite tungstenoxide fine particles according to the present invention, the compositetungsten oxide fine particle dispersed powders obtained after removal ofthe solvent from the near-infrared absorbing material fine particledispersion liquid were used. Then an X-ray diffraction pattern of thecomposite tungsten oxide fine particles was measured by a powder X-raydiffraction method (0-20 method) using a powder X-ray diffractionapparatus (X′Pert-PRO/MPD manufactured by Spectris Corporation,PANalytical). The size of the crystallite contained in the fine particlewas measured from the resulting X-ray diffraction pattern and analysisby the Rietveld method.

The dispersed particle size of the composite tungsten oxide fineparticle in the near-infrared absorbing material fine particledispersion according to the present invention was measured from theimage (×20,000) of the thinned sample of the near-infrared absorbingmaterial fine particle dispersion by a transmission electron microscope(HF-2200 manufactured by Hitachi, Ltd.) using an image analysis.

Further, visible light transmittance and solar transmittance of thenear-infrared absorbing polypropylene resin molded article containing Cstungsten oxide fine particles were measured based on JIS R 3106:1998using a spectrophotometer U-4100 manufactured by Hitachi, Ltd. The solartransmittance is an index indicating near-infrared absorptionperformance.

Example 1

In 6.70 kg of water, 7.43 kg of cesium carbonate (Cs₂CO₃) was dissolvedto obtain a solution. The solution was added to 34.57 kg of tungsticacid (H₂WO₄) and sufficiently stirred and mixed, and thereafter driedwhile stirring (the molar ratio between W and Cs is equivalent to1:0.33). The dried product was heated while supplying 5% by volume of H₂gas using N₂ gas as a carrier, and fired at a temperature of 800° C. for5.5 hours, and thereafter, the supply gas was switched to N₂ gas only,and the temperature was lowered to room temperature to obtain Cstungsten oxide fine particles (a) as the composite tungsten oxide fineparticles.

15% by mass of the Cs tungsten oxide fine particles (a), 12% by mass ofan acrylic polymer dispersant having an amine-containing group as afunctional group (an acrylic dispersant having an amine value of 48 mgKOH/g and a decomposition temperature of 250° C.) (referred to as“dispersant (a)” hereafter), and 73% by mass of toluene were weighed, 60g in total, and charged into a paint shaker (manufactured by Asada IronWorks Co., Ltd.) containing 240 g of 0.3 mmφ ZrO₂ beads, and thereaftersubjected to pulverization/dispersion treatment for 24 hours to preparea near-infrared absorbing material fine particle dispersion liquid intoluene (A-1 liquid).

The dispersed particle size of the near-infrared absorbing material fineparticle (Cs tungsten oxide fine particle (a)) in (A-1 liquid) was 72.4nm.

The crystallite size of the Cs tungsten oxide fine particle (a) in thedispersed powder after removal of the solvent from (A-1 liquid) was 25nm.

Further, 20 g of dispersant (a) was added to (A-1 liquid) to obtain anear-infrared absorbing material fine particle dispersion liquid intoluene (A-2 liquid).

The solvent was removed from (A-2 liquid) with a vacuum heating andstirring crusher (manufactured by ISHIKAWA KOJO Co., Ltd.) to obtain Cstungsten oxide fine particle dispersed powders (b).

Then, 0.5% by mass of the resulting Cs tungsten oxide fine particledispersed powder (b), 0.2% by mass of a resin modifier UMEX 1001(manufactured by SANYOKASEI CO., LTD.) as the modified polyolefin, andpolypropylene resin pellets as the polypropylene resin were mixed andmelt-kneaded at 260° C. using a twin-screw extruder, extruded from T dieto obtain an infrared absorbing fine particle dispersion according toExample 1 in which Cs tungsten oxide fine particles were uniformlydispersed throughout the polypropylene resin, and a near-infraredabsorber (e) according to Example 1 molded into a thickness of 0.6 mmwas further obtained.

The dispersed particle size of the Cs tungsten oxide fine particle inthe obtained infrared absorbing material fine particle dispersionaccording to Example 1 was 92.2 nm, and the optical properties of thenear-infrared absorber (e) were measured to find that the solartransmittance was 33.8% when the visible light transmittance was 67.1%.Table 1 illustrates the results.

Example 2

In the same manner as in Example 1 except that the addition amount ofthe polyolefin-based resin modifier UMEX 1001 (manufactured bySANYOKASEI CO., LTD.) was 0.5% by mass, the infrared absorbing materialfine particle dispersion according to Example 2 and further thenear-infrared absorber (f) were obtained.

The dispersed particle size of the Cs tungsten oxide fine particles inthe obtained infrared absorbing material fine particle dispersionaccording to Example 2 was 95.1 nm, and the optical properties of thenear-infrared absorber (f) were measured to find that the solartransmittance was 30.7% when the visible light transmittance was 62.6%.Table 1 illustrates the results.

Example 3

In the same manner as in Example 1 except that the addition amount ofthe polyolefin-based resin modifier UMEX 1001 (manufactured bySANYOKASEI CO., LTD.) was 1.5% by mass, the infrared absorbing materialfine particle dispersion according to Example 3 and further thenear-infrared absorber (g) were obtained.

The dispersed particle size of the Cs tungsten oxide fine particle inthe obtained infrared absorbing material fine particle dispersionaccording to Example 3 was 115.1 nm, and the optical properties of thenear-infrared absorber (g) were measured to find that the solartransmittance was 33.9% when the visible light transmittance was 67.4%.Table 1 illustrates the results.

Example 4

In the same manner as in Example 1 except that the addition amount ofthe polyolefin-based resin modifier UMEX 1001 (manufactured bySANYOKASEI CO., LTD.) was 5.0% by mass, the infrared absorbing materialfine particle dispersion according to Example 4 and further thenear-infrared absorber (h) were obtained.

The dispersed particle size of the Cs tungsten oxide fine particle inthe obtained infrared absorbing material fine particle dispersionaccording to Example 4 was 126.6 nm, and the optical properties of thenear-infrared absorber (h) were measured to find that the solartransmittance was 32.7% when the visible light transmittance was 65.8%.Table 1 illustrates the results.

Example 5

The mixture was obtained by mixing 0.5% by mass of the Cs tungsten oxidefine particle dispersed powders (b) obtained in the same manner as inExample 1, 1.5% by mass of HI-WAX HW NP0555A (manufactured by MitsuiChemicals, Inc.) which is an ethylene-propylene copolymer as themodified polyolefin, and polypropylene resin pellets as thepolypropylene resin. The obtained mixture was melt-kneaded at 260° C.using a twin-screw extruder, and extruded from T die to obtain aninfrared absorbing fine particle dispersion according to Example 5 inwhich Cs tungsten oxide fine particles were uniformly dispersedthroughout the polypropylene resin, and a near-infrared absorber (i)according to Example 5 molded in the thickness of 0.6 mm was furtherobtained in which Cs tungsten oxide fine particles were uniformlydispersed throughout the polypropylene resin.

The dispersed particle size of the Cs tungsten oxide fine particle inthe obtained infrared absorbing material fine particle dispersionaccording to Example 5 was 132.2 nm, and the optical properties of thenear-infrared absorber (i) were measured to find that the solartransmittance was 35.8% when the visible light transmittance was 68.6%.Table 1 illustrates the results.

Comparative Example 1

In the same manner as in Example 1, except that a resin modifier as themodified polyolefin was not used during melt-kneading of the mixture ofthe Cs tungsten oxide fine particle dispersed powder and thepolypropylene resin pellets which were the polypropylene resin at 260°C. using the twin-screw extruder, the infrared absorbing material fineparticle dispersion according to Comparative Example 1 was obtained, andthe near-infrared absorber (j) was further obtained.

The dispersed particle size of the Cs tungsten oxide fine particle inthe obtained infrared absorbing material fine particle dispersionaccording to Comparative Example 1 was 229.2 nm, and the opticalproperties of the near-infrared absorber (j) were measured to find thatthe solar transmittance was 45.2% when the visible light transmittancewas 68.7%. Table 1 illustrates the results.

Dispersed particle Composition size of Near- near- infrared infraredSample absorbing absorbing Optical properties Near- material ModifiedPoly- material Visible light Solar infrared fine particles polyolefin*propylene fine particle transmittance transmittance absorber (mass %)(mass %) resin (nm) (%) (%) Example 1 e 0.5 0.2 Balance 92.2 67.1 33.8Example 2 f 0.5 0.5 Balance 95.1 62.6 30.7 Example 3 g 0.5 1.5 Balance115.1 67.4 33.9 Example 4 h 0.5 5.0 Balance 126.6 65.8 32.7 Example 5 i0.5 1.5 Balance 132.2 68.6 35.8 Comparative j 0.5 — Balance 229.2 68.745.2 Example 1 Note: Modified polyolefin* means a polyolefin compoundwith maleic anhydride introduced therein.

SUMMARY

From the result illustrated in Table 1, it is found that thenear-infrared absorbers according to Examples 1 to 5 in which thecomposite tungsten oxide fine particles are dispersed in thepolypropylene resin containing the modified polyolefin modified with oneor more kinds selected from maleic anhydride and carboxylic anhydrideexhibit higher near-infrared absorption property and excellent opticalproperties compared to the near-infrared absorber according toComparative Example 1 which does not contain the modified polyolefin.

The invention claimed is:
 1. A near-infrared absorbing material fineparticle dispersion, comprising; composite tungsten oxide fineparticles, and modified polyolefin modified with one or more kindsselected from maleic anhydride and carboxylic anhydride, inpolypropylene resin, wherein the composite tungsten oxide fine particlesare represented by a general formula MxWyOz in which M is one or moreelements selected from Cs and Rb, W is tungsten, O is oxygen, and x, y,and z satisfy 0.20≤x/y≤0.37 and 2.2≤z/y≤3.0, the composite tungstenoxide fine particles have a hexagonal crystal structure, a crystallitesize of the composite tungsten oxide fine particles is 10 nm or more and70 nm or less, a crystallite of the composite tungsten oxide fineparticles is a single crystal, an amorphous phase volume ratio is 50% orless in the composite tungsten oxide fine particles, the amorphous phaseexists on an outer periphery of each of the composite tungsten oxidefine particles, a dispersed particle size of the composite tungstenoxide fine particles is 10 nm or more and 200 nm or less, an additionamount of the modified polyolefin is 1 part by mass or more and 2,000parts by mass or less with respect to 100 parts by mass of thenear-infrared absorbing material fine particles, the near-infraredabsorbing material fine particle dispersion has transparency in avisible light region, and a haze value of the near-infrared absorbingmaterial fine particle dispersion is 10% or less at visible lighttransmittance of 85% or less.
 2. The near-infrared absorbing materialfine particle dispersion according to claim 1, wherein a weight averagemolecular weight of the modified polyolefin is 1,000 or more and 100,000or less.
 3. The near-infrared absorbing material fine particledispersion according to claim 1, wherein an acid number of the modifiedpolyolefin is 1 mgKOH/mg or more and 150 mgKOH/mg or less.
 4. Thenear-infrared absorbing material fine particle dispersion according toclaim 1, wherein a surface of the composite tungsten oxide fineparticles is coated with an oxide containing one or more elementsselected from Si, Ti, Zr, and Al.
 5. A near-infrared absorber, whereinthe near-infrared absorbing material fine particle dispersion accordingto claim 1 is diluted and melt-kneaded with polypropylene resin or aheterogeneous thermoplastic resin having compatibility with thepolypropylene resin, and molded into any one shape selected from aplate, a film, and a thin film.
 6. A near-infrared absorber laminate,comprising the near-infrared absorber according to claim 5 laminated ona base material.
 7. A laminated structure for near-infrared absorption,wherein the near-infrared absorber laminate according to claim 6 isopposed to a laminated plate selected from sheet glass, a plastic plate,and a plastic plate containing fine particles having a near-infraredabsorption function, or is present between two or more laminated platesselected from the sheet glass, the plastic plate, and the plastic platecontaining fine particles having the near-infrared absorption function.8. A laminated structure for near-infrared absorption, comprising thenear-infrared absorber according to claim 5 present between two or morelaminated plates selected from sheet glass, a plastic plate, and aplastic plate containing fine particles having a near-infraredabsorption function.
 9. The near-infrared absorbing material fineparticle dispersion according to claim 1, wherein the crystallite sizeof the composite tungsten oxide fine particles is 25 nm.
 10. Thenear-infrared absorbing material fine particle dispersion according toclaim 1, wherein the dispersed particle size of the composite tungstenoxide fine particles is 92.2 nm or more and 132.2 nm or less.
 11. Thenear-infrared absorbing material fine particle dispersion according toclaim 1, wherein the addition amount of the modified polyolefin is 40parts by mass or more and 1,000 parts by mass or less with respect to100 parts by mass of the near-infrared absorbing material fineparticles.